6 CONTENTS. 



Page. 



Dissemination of the uredospore 53 



Methods of dissemination 53 



Viability of the uredospore 55 



First appearance of rusts in the spring 55 



Epidemics 58 



General discussion 58 



Conditions favorable for an epidemic 58 



Climatological conditions in relation to rusts in 1903, 1904, and 1905 60 



Precipitation 60 



Relative humidity 63 



Temperature 63 



Prevention of rusts 66 



Spraying experiments 66 



Soil and soil treatments 68 



Resistant varieties 70 



Causes of resistance 70 



Selection and breeding of resistant varieties 71 



Methods used in selection and breeding 72 



Summary 73 



Bibliography 79 



Index 83 



LLUSTRATI0NS 



PLATE. 



Pag*. 

 Plate I. Stem rust of wheat on wheat culms, showing various degrees of 



attack Frontispiece. 



TEXT FIGURES. 



Fig. 1. Precipitation chart, showing the average monthly departure from 



normal in several States in 1903, 1904, and 1905 62 



2. Temperature chart, showing the average monthly departure from 



normal in several States in 1903, 1904, and 1905 65 



216 



